1. Field of the Invention
This invention relates to a vehicle interior illumination lamp for mounting within a room of a vehicle.
2. Related Art
Generally, a vehicle has an interior illumination lamp mounted on a ceiling thereof.
As shown in FIG. 7, one such known interior illumination lamp comprises a function part A which is attached to a roof panel (interior member) 101 (covering a vehicle body panel (note shown)) from that side facing a vehicle body panel, and is partially exposed to the inside of a vehicle room through an opening portion 102 in the roof panel 101, and a design part B which is attached to the roof panel 101 from the inside of the vehicle room to cover the opening portion 102, and is combined with the function part A (see, for example, JP-A-2002-79879 (Pages 15 to 17, FIG. 19)).
The function part A includes a bulb 103 serving as a light source, and a switch unit 104 for supplying and interrupting electric power relative to the bulb 103. A cable 115, such as an FFC (flexible flat cable), is connected to a cable connection portion (not shown) of a switch circuit of the switch unit 104. A switch lever 105 for supplying and interrupting electric power relative to the bulb 103 is provided at the switch unit 104.
A pair of elastic retaining piece portions 111, formed respectively on opposite side portions of the function part A, are brought into engagement with a peripheral edge portion of the opening portion 102 from the inside of the vehicle room, and at the same time a plurality of support projecting piece portions 112, formed at front and rear ends of the function part A, are brought into abutting engagement with the peripheral edge portion of the opening portion 102 from that side facing the vehicle body panel, thereby mounting the function part A on the roof panel 101.
The design part B includes a housing 108 which is formed into a light-transmitting lens-like configuration, and has retaining projections 114, and this housing 108 is attached to the root panel 101 to cover the opening portion 102 from the inside of the vehicle room, with the retaining projections 114 engaged respectively in engagement holes 113 formed in the peripheral edge portion of the opening portion 102.
A switch knob 106 is mounted in a suspended manner on the housing 108 through a pair of retaining claws engaged with that surface of a peripheral edge portion of a slide groove 109 facing the vehicle body panel, so that the switch knob 106 can slidingly move along the slide groove 109. A pair of limitation projections 110 are formed on and project from the housing 108, and are disposed adjacent to the slide groove 109 in the housing 108, and these limitation projections 110 hold the switch unit 104 therebetween in the direction of sliding movement of the slide knob 106 so as to prevent the switch unit 104 (the function part A) from being displaced relative to the housing 108 in the direction of sliding movement of the slide knob 106
The function part A and the design part B are combined together through the roof panel 101, and in this condition the switch knob 106 of the design part B is engaged at its engagement portion 107 with the switch lever 105 of the switch unit 104. When the switch knob 106 is pressed or operated in its sliding direction, the switch lever 105 is moved in unison with the switch knob 106 so as to supply and interrupt electric power relative to the bulb 103.
In the vehicle interior illumination lamp disclosed in the above Patent Literature 1, the switch unit 104 (which directly receives a pressing force when the switch knob 106 is pressed or operated) is prevented merely by the pair of limitation projections 110 on the housing 108 from displacement in the direction of sliding movement of the switch knob 106. Namely, that side or surface of the switch unit 104, facing the vehicle body panel, is not directly held by either of the roof panel 101 and the housing 108 of the design part B. Therefore, in case an urging force, urging the switch knob 106 toward the switch unit 104, is applied when the switch knob 106 is operated, there has been a possibility that the switch unit 104, directly receiving this pressing force, is displaced toward the vehicle body panel, that is, in a direction away from the housing 108, so that the whole of the function part A is disengaged from the design part B (that is, the function potion A is brought out of engagement with the roof panel 101).
When the function part A is thus disengaged from the design part B, the engagement of the switch lever 105 with the switch knob 106 is canceled, and therefore the switch lever 105 can not be operated through the switch knob 106, thus inviting a so-called malfunction, that is, a failure to supply and interrupt electric power relative to the bulb 103.
And besides, there has been a fear that the function part A and the design part B are improperly assembled together in a process of mounting of the interior illumination lamp on the vehicle, since the function part A is liable to be disengaged from the design part B when the switch knob 106 is pressed toward the vehicle body panel.